Hi Chris,

Below is a screen capture demonstrating merging joint-driven (weighted) objects into one. If merged directly, the Joints are missing)
I'm sure process will look simple after you explore it on the example file.

Here is a 60-second clip going through it. I think it is a good idea to keep the Joints and objects in the Object manager in the same order if they are not just copies, like Joints 1, 2, 3 (or 3, 2, 1), and the objects as well 1,2,3, or 3,2,1, etc.
https://stcineversityprod02.blob.core.windows.net/$web/Cineversity_Forum_Support/2024_Clips_DRS/20240422_MergeJoint-Weight.mp4
Test file:
CV4_2024_drs_24_ANmc_11.c4d
Connected
CV4_2024_drs_24_ANmc_12.c4d

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As a side note: (Alternatives)

An easy way to work on mechanical setups is to have PoseMorph working on them while the parts' axis is the animation's axis. However, that would work for Joints as well. These Pose Morphs, even on different objects, can be connected to the user Data Slider and animated from this "central" mixer created with user Data and XPresso.

Or:

Have character definitions bring matching hierarchies into sync.

Or:
Joints can also be placed in XPresso Lists and "Iterated" throughout to work in sync.

If this doesn't work, we look at your file 🙂

Cheers